I'm assuming you are on Wordpress. You should be able to add more widgets by going to appearance and viewing the widgets you have available. Of course this will depend on the version and current configuration of your Wordpress site.

This post describes how to add a side bar to a theme (not sure if that will be specific to your situation however it may point you in the right direction).

You can choose what widgets display on each page within the "screen option" you can find this on the "new post" "new page" Area just above the title, if I remember correct you need a plugin called dynamic widgets.

Yeah but this is a plugin which when the widget is dragged over into the side bar widget slot it displays everywhere. Unlike ad injection where u can select where you want it to show. This plugin doesnt allow me to choose where to show it. Its the facebook like box plugin

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